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Activation of a potassium outward current by zymosan and opsonized zymosan in mouse peritoneal macrophages
F Berger1, U Borchard, D Hafner
1Institut für Pharmakologie, Heinrich-Heine-Universität Düsseldorf, Germany.
Abstract:
The effects of zymosan and human serum opsonized zymosan on membrane currents of adherent mouse peritoneal macrophages which had been cultured for 5 to 20 days were investigated with the whole-cell voltage-clamp technique. Both stimuli activated an outward current. The outward current activation was transient and lasted about 5 min. In solutions with 10 or 50 mmol/l extracellular potassium concentration the activation of an outwardly directed current occurred at test potentials positive to the respective potassium equilibrium potential. This particle-induced current resembled a calcium-activated potassium current which could be activated with the calcium ionophore A 23187 and with platelet activating factor. The order of maximal responses (test potential + 55 mV, amplitude given as percentage of the respective control) was: 0.1 mumol/l platelet activating factor (222 +/- 36%, n = 8, P < 0.01) > 1 mumol/l A 23187 (190 +/- 24%, n = 11, P < 0.01) > 900 micrograms/ml opsonized zymosan (134 +/- 7%, n = 22, P < 0.01) > 900 micrograms/ml zymosan (116 +/- 5%, n = 21, P < 0.01). The lower efficiency of zymosan as compared to opsonized zymosan is explained in part by a lower percentage of responding cells which was 48% for zymosan and 73% for opsonized zymosan. Macrophages which were pretreated with particles showed a greater reactivity to calcium as compared to untreated cells.(ABSTRACT TRUNCATED AT 250 WORDS)
Insights
Zymosan and opsonized zymosan activate outward membrane currents in mouse macrophages, resembling calcium-activated potassium currents. Opsonized zymosan showed greater efficiency in activating these currents.
Area of Science:
- Immunology
- Cell Physiology
Background:
- Macrophages play a crucial role in the innate immune system.
- Membrane currents are essential for cellular functions, including immune responses.
Purpose of the Study:
- To investigate the effects of zymosan and opsonized zymosan on membrane currents in mouse peritoneal macrophages.
- To characterize the nature of the particle-induced membrane currents.
Main Methods:
- Whole-cell voltage-clamp technique applied to cultured mouse peritoneal macrophages.
- Stimulation with zymosan, opsonized zymosan, calcium ionophore A 23187, and platelet-activating factor.
- Analysis of outward current activation and amplitude at various extracellular potassium concentrations.
Main Results:
- Both zymosan and opsonized zymosan transiently activated an outward membrane current.
- The induced current exhibited characteristics of a calcium-activated potassium current.
- Opsonized zymosan was more effective than non-opsonized zymosan in activating the outward current.
- Pretreatment with particles enhanced macrophage reactivity to calcium.
Conclusions:
- Zymosan and opsonized zymosan modulate macrophage membrane currents, likely via calcium-dependent pathways.
- Opsonization enhances the stimulatory effect of zymosan on macrophage membrane currents.
- These findings contribute to understanding macrophage activation and ion channel function during immune responses.